Abstract: Thermochemical energy storage （TCES） systems based on calcium looping （CaL） technology can be integrated with third-generation concentrating solar power plants （CSP） to achieve efficient utilization of solar-thermal energy. However, conventional CaO-based thermochemical energy storage materials face critical challenges such as low reaction activity and poor stability in cyclic heat storage/release performance, which severely restrict the improvement of system efficiency. To develop high-performance CaO-based thermochemical energy storage materials, a spray pyrolysis method based on dual-fluid atomization technology was proposed, employing an aqueous solution of calcium nitrate and citric acid as the precursor to prepare porous hollow CaO microspheres. First, the atomization characteristics of precursor solutions with different flow rates （10～20 mL/min） under varying atomizing gas flow rates （10～30 L/min） were investigated using a spray laser particle size analyzer. It was found that lower solution flow rates and higher atomizing gas flow rates result in smaller Sauter mean diameter （S_MD） and narrower particle size distribution （span） of the spray. However, when the atomizing gas flow rate exceeds 20 L/min, both the S_MD and particle size distribution of the spray tend to stabilize. Based on these results, a precursor solution flow rate of 10 mL/min was selected for spray pyrolysis. The effects of the air-liquid ratio （ALR, 1000～3000） on the crystallite size, particle size distribution, micromorphology, cyclic heat storage/release performance, and pore structure parameters of the synthesized CaO microspheres were studied using X-ray diffractometer （XRD）, powder laser particle size analyzer, scanning electron microscope （SEM）, simultaneous thermal analyzer （STA）, and nitrogen adsorption−desorption tests. The results show that the S_MD of CaO microspheres decreases with increasing ALR, consistent with the variation law of precursor solution atomization characteristics. The cyclic heat storage/release performance exhibits a trend of first increasing and then decreasing with increasing ALR, reaching the optimal performance at an ALR of 2000. Under this condition, the prepared CaO microspheres have an S_MD of 12.5 μm, a high specific surface area of 31.63 m²/g, a carbonation conversion of 92.68% in initial cycle, and a cumulative energy storage density of 46.13 kJ/g after 30 cycles, 2.32 times higher than that of analytical pure CaO.